<!-------- @HEADER
 !
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 !
 !  Zoltan Toolkit for Load-balancing, Partitioning, Ordering and Coloring
 !                  Copyright 2012 Sandia Corporation
 !
 ! Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
 ! the U.S. Government retains certain rights in this software.
 !
 ! Redistribution and use in source and binary forms, with or without
 ! modification, are permitted provided that the following conditions are
 ! met:
 !
 ! 1. Redistributions of source code must retain the above copyright
 ! notice, this list of conditions and the following disclaimer.
 !
 ! 2. Redistributions in binary form must reproduce the above copyright
 ! notice, this list of conditions and the following disclaimer in the
 ! documentation and/or other materials provided with the distribution.
 !
 ! 3. Neither the name of the Corporation nor the names of the
 ! contributors may be used to endorse or promote products derived from
 ! this software without specific prior written permission.
 !
 ! THIS SOFTWARE IS PROVIDED BY SANDIA CORPORATION "AS IS" AND ANY
 ! EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 ! IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 ! PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SANDIA CORPORATION OR THE
 ! CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 ! EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 ! PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 ! PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 ! LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 ! NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 ! SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 !
 ! Questions? Contact Karen Devine	kddevin@sandia.gov
 !                    Erik Boman	egboman@sandia.gov
 !
 ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 !
 ! @HEADER
-------> 
<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
   <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
   <meta name="GENERATOR" content="Mozilla/4.7 [en] (X11; U; SunOS 5.6 sun4m) [Netscape]">
   <meta name="sandia.approved" content="SAND99-1376">
   <meta name="author" content="karen devine, kddevin@sandia.gov">
   <title> Zoltan Developer's Guide:  Hash function</title>

</head>
<body bgcolor="#FFFFFF">

<div align=right><b><i><a href="dev.html">Zoltan Developer's Guide</a>&nbsp;
|&nbsp; <a href="dev_services_time.html">Next</a>&nbsp; |&nbsp; <a href="dev_services_objlist.html">Previous</a></i></b></div>

<!------------------------------------------------------------------------->

<h2>
Hash Function</h2>
Zoltan provides a hash function for global and local IDs. The hash function
computes a non-negative integer value in a certain range<i> </i>from an
ID.
<blockquote><b><a href="#Zoltan_Hash">Zoltan_Hash</a></b>&nbsp; : hash a global
or local ID into non-negative integers</blockquote>

<!------------------------------------------------------------------------->
<hr>
<a NAME="Zoltan_Hash"></a>
<hr>
unsigned int<b> Zoltan_Hash</b>(
<b><a href="../ug_html/ug_usage.html#Data Types for Object IDs">ZOLTAN_ID_PTR
</a></b><i>key</i>,
int <i>num_id_entries</i>, unsigned int <i>n</i>);&nbsp;
<hr>
<b>Zoltan_Hash </b>computes a hash value for a global or local ID. Note
that this hash function has been optimized for 32-bit integer systems,
but should&nbsp; work on any machine. The current implementation uses a
simple multiplicative hash function based on Don Knuth's golden ratio method;
see <i>The Art of&nbsp; Computer Programming,</i> vol. 3.
<br>&nbsp;
<table WIDTH="100%" >
<tr VALIGN=TOP>
<td VALIGN=TOP WIDTH="20%"><b>Arguments:</b></td>

<td WIDTH="80%"></td>
</tr>

<tr VALIGN=TOP>
<td VALIGN=TOP>&nbsp;&nbsp;&nbsp; <i>key</i></td>

<td>A pointer to the ID to be hashed.</td>
</tr>

<tr VALIGN=TOP>
<td>&nbsp;&nbsp;&nbsp; <i>num_id_entries</i></td>

<td>The length of the ID (as given by <b><a href="../ug_html/ug_param.html#NUM_GID_ENTRIES">NUM_GID_ENTRIES</a></b>
or <b><a href="../ug_html/ug_param.html#NUM_LID_ENTRIES">NUM_LID_ENTRIES</a></b>).</td>
</tr>

<tr VALIGN=TOP>
<td VALIGN=TOP>&nbsp;&nbsp;&nbsp; <i>n</i></td>

<td>The computed hash value will be between 0 and <i>n</i>-1.&nbsp;</td>
</tr>

<tr VALIGN=TOP>
<td><b>Return Value:</b></td>

<td></td>
</tr>

<tr VALIGN=TOP>
<td>&nbsp;&nbsp;&nbsp; unsigned int</td>

<td>The hash value (between 0<i> </i>and <i>n</i>-1).&nbsp;</td>
</tr>
</table>

<p>
<!------------------------------------------------------------------------->
<hr WIDTH="100%">
<br>[<a href="dev.html">Table of Contents</a>&nbsp; |&nbsp; <a href="dev_services_time.html">Next:&nbsp;
Timing Routines</a>&nbsp; |&nbsp; <a href="dev_services_objlist.html">Previous:&nbsp;
Object List Function</a>&nbsp; |&nbsp; <a href="https://www.sandia.gov/general/privacy-security/index.html">Privacy and Security</a>]
</body>
</html>
